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Image forming apparatus using common AC voltage source for plural charging members and photosensitive members

a technology of photosensitive members and forming apparatus, which is applied in the direction of electrographic process apparatus, instruments, corona discharge, etc., can solve the problems of large number of voltage sources, device upsizing, and ac charging type charging devices that do not work with charging ac voltag

Inactive Publication Date: 2014-08-12
CANON KK
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

If the charging AC voltage is too low, the photosensitive member is not charged up to a desired potential or the charging of the photosensitive member is not uniform with the result that sandpaper like background or foggy background (deposition of the toner on the non-image portion on which the toner is not to be deposited) is produced.
On the other hand, because of the existence of the minimum charging AC voltage (Vmin) necessary for uniformly charging the photosensitive member, the AC charging type charging device does not work with the charging AC voltage not higher than the minimum level.
However, in the tandem type image forming apparatus, if the image forming stations are provided with respective AC voltage sources to apply the charging AC voltages within the proper ranges to the charging members of the image forming stations, respectively, the number of the voltage sources is large.
If the number of the voltage sources increases, the device is upsized, and the weight thereof increases with the result of cost increase.
With single commonality of the voltage source, however, the same charging AC voltages are applied to the image forming stations, and therefore, when charging AC voltages within the proper ranges are different depending on the image forming stations, one or some of the image forming stations are not supplied with the proper charging AC voltages.
On the other hand, charging non-uniformity of the photosensitive member occurs in the magenta image forming station with the result of image defect such as fog.

Method used

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  • Image forming apparatus using common AC voltage source for plural charging members and photosensitive members
  • Image forming apparatus using common AC voltage source for plural charging members and photosensitive members
  • Image forming apparatus using common AC voltage source for plural charging members and photosensitive members

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Experimental program
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embodiment 1

1. General Arrangement and Operation of Image Forming Apparatus

[0035]FIG. 1 shows a general arrangement of an image forming apparatus 100 according to Embodiment 1 of the present invention. The image forming apparatus 100 according to this embodiment is a tandem type full-color image forming apparatus using an electrophotographic system.

[0036]The image forming apparatus 100 comprises a plurality of image forming stations, namely, first, second, third and fourth image forming stations Sa, Sb, Sc, Sd for forming yellow (Y), magenta (M), cyan (C) and black (Bk) images. Such four image forming stations Sa, Sb, Sc, Sd are arranged in line at constant intervals along a moving direction of an image carrying surface of an intermediary transfer member as a transfer member which will be described hereinafter in detail. In this embodiment, a voltage source is common for the first, second and third image forming stations Sa, Sb, Sc to apply the voltages to the charging members therein.

[0037]In ...

embodiment 2

[0110]Another embodiment will be described. The fundamental structures and operations of the image forming apparatus of this embodiment are the same as those of Embodiment 1. In the description of this embodiment, the same reference numerals as in Embodiment 1 are assigned to the elements having the corresponding functions in this embodiment, and the detailed description thereof is omitted for simplicity.

[0111]In Embodiment 1, the use situation of the photosensitive drum 1 is represented by the cumulated number of image formations, on the basis of which the electric resistance of the variable resistor 40 is adjusted. As shown in FIG. 3 of the operational sequence of the image forming apparatus 100, the image forming operation includes the multiple pre-rotation period, the sheet interval period and the post-rotation step. Therefore, the scraping amount of the photosensitive drum 1 may be different between when the image formations are carried out continuously on 100 sheets and when t...

embodiment 3

[0132]A further embodiment will be described. The fundamental structures and operations of the image forming apparatus of this embodiment are the same as those of Embodiment 1. In the description of this embodiment, the same reference numerals as in Embodiment 1 are assigned to the elements having the corresponding functions in this embodiment, and the detailed description thereof is omitted for simplicity.

[0133]In Embodiment 1, the use situation of the photosensitive drum 1 is represented by the cumulated number of image formations, on the basis of which the electric resistance of the variable resistor 40 is adjusted. As shown in FIG. 3 of the operational sequence of the image forming apparatus 100, the image forming operation in Embodiment 2 includes the multiple pre-rotation period, the sheet interval period and the post-rotation step. Therefore, the scraping amount of the photosensitive drum 1 may be different between when the image formations are carried out continuously on 100...

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PUM

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Abstract

An image forming apparatus includes photosensitive drums; drum charging members, an AC voltage source for outputting an AC voltage commonly to at least two of the charging members; AC voltage control devices for the charging members; variable resistors connected between the AC voltage source and the at least two charging members, respectively; a use situation detecting unit for detecting use situations of the drums, respectively; and an adjusting unit for adjusting electric resistances of the variable resistors, respectively. The adjusting unit adjusts the electric resistances of the resistors in accordance with the detection results of the use situation detecting unit such that the discharge currents applied to the at least two charging members are within predetermined ranges, respectively.

Description

FIELD OF THE INVENTION AND RELATED ART[0001]The present invention relates to an image forming apparatus such as an electrophotographic type copying machine, printer or facsimile machine.[0002]A tandem type electrophotographic type image forming apparatus is known in which image forming stations having respective photosensitive members are arranged in line along a moving direction of a recording material carrying member or an intermediary transfer member. The image forming stations of the tandem type image forming apparatus include yellow, magenta, cyan and black image forming stations, for example, toner images formed on the photosensitive members of the image forming stations are sequentially transferred onto the recording material or an intermediary transfer member carried on the recording material carrying member, superimposedly. In each image forming station, the surface of the photosensitive member is charged uniformly, and thereafter, it is exposed to light in accordance with ...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): G03G15/02G03G15/00
CPCG03G15/0266
Inventor SHIBUYA, KENICHI
Owner CANON KK